Bridge Structure and Dimensions
Miyoshi Bridge measures approximately 243.5 meters in total length, with a central span of 139.9 meters. When it first opened in 1927, its suspension design relied on main cables secured by large anchorage structures at either end of the bridge.
Those anchorages remain visible today, although they no longer serve their original structural purpose. Following major repairs completed in August 1989, the bridge became an arch bridge. Its distinctive structure reflects the engineering challenges involved in adapting an aging bridge while preserving its existing deck.
From Ferry Crossings to a Permanent Bridge
Before Miyoshi Bridge was built, ferry services were an important means of crossing the Yoshino River and other waterways in Tokushima Prefecture. However, ferries could not operate during floods, and capsizing accidents sometimes resulted in loss of life. A safer and more dependable crossing was urgently needed.
According to Tokushima Prefecture statistics from 1891, there were 154 ferry crossing points across the prefecture, including 125 along the Yoshino River. The completion of Miyoshi Bridge in 1927 represented an important step toward safer transportation and a new era of river crossings for the local community.
The 1987 Cable Damage and Major Reconstruction
In 1987, severe corrosion and partial damage were discovered in the bridge’s main suspension cables. Because these cables were essential to supporting the structure, the damage raised concerns about the bridge’s safety, and vehicle traffic was prohibited while engineers considered how best to repair it.
Rebuilding the bridge as a suspension bridge was considered, but geographical constraints and difficulties reusing the original anchorages made this option impractical. Engineers instead chose to convert it into an arch bridge, allowing the existing bridge deck to be retained while changing the way the structure carried its load.
From Suspension Bridge to Arch Bridge
The reconstruction began in fiscal year 1987. Rather than demolishing the existing deck, engineers installed a new arch beneath it and removed the original main cables. The project required detailed structural calculations because the change from a suspension system to an arch system significantly altered the forces acting on the bridge.
The completed structure uses an upper-deck arch design, in which the roadway sits above the supporting arch. Work was completed in August 1989, giving Miyoshi Bridge a new structural form while extending its service life.
After reconstruction, engineers conducted tests by deliberately inducing vibrations and observing the bridge’s response. The results confirmed that the new arch structure was functioning properly, allowing the bridge to continue serving the region.
A Memorial to the Original Suspension Bridge
Part of the main cable removed during the reconstruction was preserved and fashioned into a monument on the eastern bank of the Yoshino River. Photographs of the bridge in its original suspension-bridge form are also displayed there, helping visitors understand the structure’s transformation and the engineering work that saved it.
The Yoshino River Landscape
The area around Miyoshi City is characterized by mountainous terrain and deep valleys. Here, the Yoshino River flows generally from south to north, while Miyoshi Bridge crosses it on an approximately east–west alignment. The surrounding landscape helps explain the importance of a durable crossing in this rugged part of Tokushima.
In 1975, Ikeda Dam was completed downstream from Miyoshi Bridge. The bridge was not submerged by the dam project and remains in place today. Other bridges in the surrounding area include Okawa Bridge, the First Yoshino River Railway Bridge on the Dosan Line, and Ikeda Bridge, all of which contribute to the region’s transportation network.
Access
Miyoshi Bridge can be reached on foot from Minawa Station on the JR Dosan Line. Visitors exploring Miyoshi City can stop to view the bridge’s arch structure, examine the remnants of its original suspension system, and appreciate the role it has played in local transportation history.
More than simply a river crossing, Miyoshi Bridge is a reminder of the challenges faced by communities living alongside the powerful Yoshino River. Its transformation from a suspension bridge into an arch bridge makes it a worthwhile stop for travelers interested in historic infrastructure, engineering, and the landscapes of western Tokushima.